In a recent camera market, demand of an on-vehicle sensing camera, a high pixel monitoring camera and the like has increased and a further small and high-performance camera has been demanded. Further, a lens unit having high performance which is used in the camera has been required.
In a case that a tube-shaped holder which holds a lens (hereinafter, referred to as a “lens-barrel”) is made of plastic, injection molding is commonly utilized. When a circular lens-barrel (inner peripheral face) is to be formed, distortion is occurred by a flow of resin at the time of molding and its outer shape and, as a result, the inner peripheral face may be difficult to be circular and may be formed in an elliptical shape. In order to prevent this problem, a plurality of ribs is formed on the inner peripheral face and a height of each of the ribs is adjusted. As a result, the centers of the lenses are easily aligned at the time of assembling and working of a metal mold component can be simply performed. Various techniques regarding this structure have been proposed (see, for example, Japanese Patent Laid-Open No. 2016-18182 (Patent Literature 1)).
In the technique disclosed in Patent Literature 1, a plurality of alignment protruded parts (rib) formed on a tube part of a lens-barrel in a circumferential direction includes a first alignment protruded part and a second alignment protruded part whose protruding amount is different from that of the first alignment protruded part. Appropriate alignment can be attained by determining an imaginary circle corresponding to an outer periphery of a lens by using two types of alignment protruded parts having different protruding amounts (first and second alignment protruded parts).
On the other hand, an arrangement position of a gate in a lens-barrel is restricted by a demand for further miniaturization, designation of a supported portion by a cover case, designation of a threaded portion and the like. Further, recently, an integrated article of a lens-barrel and a cover case has been required. As a result, in either a single lens-barrel or an integrated article of a lens-barrel and a cover case, distortion due to a resin flow at the time of molding and distortion due to its outer shape are further easily occurred and thus the inner peripheral face is further deformed (ellipse becomes larger). Therefore, a new technique has been required. Specifically, an ellipse of an inner peripheral face becomes larger, adjustment of protruding amounts of the ribs becomes difficult. In other words, an advanced working for a metal mold component is required because circularity is secured by a plurality of ribs and heights (protruding amount) of the libs are set so as to be capable of being lightly press-fitted.